A method for determining whether nonverbal organisms like human infants are conscious, called the marker methodology, has gained attention but is fundamentally flawed. This approach uses markers thought to correlate with consciousness instead of relying on theories of consciousness. The authors argue that this method is unlike other scientific investigations because its markers are derived neither from theory nor from commonsense conceptions of the target phenomenon. They contend the marker method should be abandoned and propose using commonsense markers instead to explore infant and other forms of consciousness.
The claim that consciousness is necessary for a being to have a welfare—a view called phenomenalism—can take two forms: either consciousness is required for welfare subjecthood, or conscious beings have greater welfare capacity. The authors argue that hedonism, the most plausible source of support for either version, actually provides no support for phenomenalism. They instead discuss an alternative view, mentalism, which holds that welfare subjectivity and capacity depend on mentality more broadly, not specifically on consciousness.